MOTEGI - Jorge Lorenzo piled pressure on championship leader Valentino Rossi on Saturday as he grabbed pole position for the Japanese Grand Prix, after Alex de Angelis suffered serious injuries and memory loss in a heavy crash.

The Spaniard grabbed his fourth pole position of the season after having led all four practice sessions before clocking 1min 43.790sec in qualifying, 0.081sec faster than Yamaha team-mate Rossi. Injured defending champion Marc Marquez, who broke a bone in his left hand in a mountain-biking accident last month, shares the front row with the Yamaha duo, coming in 0.426sec slower than Lorenzo.

Earlier ART rider de Angelis came off in the fourth free practice session and was helicoptered to hospital, where doctors found fractures in three vertebrae and several ribs, as well as a bruised lung.

The San Marino rider also sustained a head injury and does not remember the accident, and will likely be taken to Italy next week, according to his team, IodaRacing.

Lorenzo said he was "very happy" with pole position as he aims to further narrow his 14-point deficit on Italian veteran Rossi, with four races left including Japan. Lorenzo has a history of outperforming his rivals at Japan's Twin Ring Motegi circuit, where he won in 2014, 2013 and 2009 and finished second in 2012 and 2011.

The track's stop-and-go layout with hard acceleration and braking points poses a major challenge for riders, many of whom suffered injuries.

Lorenzo had ice on his left shoulder after he was injured in practice on Monday. Rainfall is expected for Sunday's race and thick, dark cloud cover lowered the temperature markedly on Saturday.

Meanwhile, Rossi's mood also blackened as pole position slipped away from him in the final minutes of the qualifying when Lorenzo stormed back to the top of the timesheets. "It's a shame... because pole position is something that doesn't happen very often, especially to me," Rossi said.

"But that aside, I am satisfied about today. We worked well with the team. In the free practice, I was consistent. I was fast. We did a good strategy. I was in the right place. For sure, Jorge is always fast. We can try to stay close," the Italian said. "I know I can do a little bit better."

Marquez, standing 79 points behind Rossi in the championship battle, said his injured left hand was stopping him from riding at his full potential, allowing the sizzling Yamaha men to stay ahead. "My finger is painful, of course, it's broke. But that's OK. I can ride more or less well," said the Spaniard, the season champion in 2013 and 2014, who will take painkillers for Sunday's race. I am closer to Valentino, but still not enough," Marquez said.